The Latin name of all the major insect orders ends in “ptera”, which means “wing”, and for good reason! The majority of the thirty or so orders of insects are flighted arthropods*, and their wings help to define them both ecologically and taxonomically. It is even suggestive as to the course of their evolution!
For example, the most diverse insect orders are Coleoptera (beetles), Diptera (flies), Hymenoptera (bees, wasps, and ants), Lepidoptera (butterflies, skippers, and moths). These four orders are represented by about 600,000–795,000 species (according to Wikipedia). So I’ll briefly explain how wings help to identify these four orders, and I’ll throw in a fifth (because I think it is common and important), the Hemiptera (true bugs).
(NB: remember that the stereotypical insect anatomy includes four wings, a pair of forewings, and a pair of hindwings. It is important to know that before we start deviating from it)
Coleoptera The name of the beetle order means “sheathed wing”. It refers to the fact that the forewings on beetles have been modified into a hard carapace, or shell, which protects them. The front wings are now called “elytra”, and they have specialized hooks all along the edges that allow beetles to lock their wings together. When a beetle is threatened, it will close the elytra (folding its delicate membranous wings beneath), fold its legs under its body, tuck its antennae in, and hunker down until the danger is passed. A locked down beetle is like a tank; it is very hard to crack into.
Diptera The name of the beetle order means “two wings” and refers to the fact that all flies have only two wings instead of four. Their hindwings have been modified into small, clublike appendages known as “halteres”. The halteres, aside from being a diagnostic feature of the order, give flies Supreme Flight Manoeuverability, which allows them to flip upside down and land on the ceiling, or annoyingly dodge your swats.
Hymenoptera A little less helpfully, the name of the order of ants, bees, and wasps means “membrane wing”. Members of this order have four membranous wings, but that is not a diagnostic feature (given that other orders do also have four membranous wings). Most hymenopterans have what is known as a “wasp waist”, or a constriction between the thorax or the abdomen. The exception is the primitive hymenopterans known as sawflies (suborder Symphyta).
Lepidoptera The name of the order of butterflies, skippers, and moths means “scale wing”, referring to the often colourfully patterned scales that cover the membranous wings of these insects. The scales rub off like dust or powder if you touch the wings, which you may or may not have experience with from childhood. There are some notable exceptions (i.e. the clearwings).
Hemiptera The name of the order of true bugs means “half wing” and refers to those members of this order whose forewings are divided into both membranous and hard parts. The modified forewings are then known as “hemielytra” (like partial hard wing from the beetles). However, this order now includes members of what used to be a separate order, the Homoptera. These insects have four whole wings, and therefore do not fit the diagnostic feature of half wing. In other words, all insects with hemielytra are hemipterans but not all hemipterans have hemielytra.
*save the springtails (Collembola)**, mantises (Mantodea), cockroaches (Blattodea), dragonflies and damselflies (Odonata), termites (Termitoidae), webspinners (Embiidina), bristletails (Microcoryphia), silverfish (Zygentoma), and chewing and sucking lice (Mallophaga and Anoplura), but we’ll save them for another post!
**some would argue that Collembola does not technically fall in the class insecta, but in the subphylum hexapoda. It is up for debate!